Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various layers using lithography to form circuit components and elements thereon.
A transistor is an element that is utilized extensively in semiconductor devices. There may be millions of transistors on a single integrated circuit (IC), for example. A common type of transistor used in semiconductor device fabrication is a metal oxide semiconductor field effect transistor (MOSFET), as an example. A transistor typically includes a gate dielectric disposed over a channel region, and a gate formed over the gate dielectric. A source region and a drain region are formed on either side of the channel region within a substrate or workpiece.
One challenge in the fabrication of transistors is the patterning of transistor gates. The overlapping regions of transistor gates with underlying isolation regions and active regions formed in a workpiece are particular areas of concern in some applications, because it is important for the various material layers to align correctly in order for the device to operate properly.
Furthermore, punch-through or undesired removal of top portions of a workpiece and other material layers during etch processes used to pattern transistor gates and other features may degrade device performance or lead to device failures.
Thus, what are needed in the art are improved methods of patterning transistor gates and other features of semiconductor devices.